TWO DESTRUCTIVE 
TEXAS ANTS 



WD. HUNTER 

In Charge of Southern Field Crop 
Insect Investigations 



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UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT CIRCULAR 148? 



Contribution from the Rureau of Entomology 
L. O. HOWARD, Chief 



Washington, D. C. 



Issued April, 1912; reprint March, 192'2 



WASHINGTON : GOVERNMENT PRINTING OFFICE : l»2J 



Monograph, 



BUREAU OF ENTOMOLOGY. 

' L. o. Howard, Entomologist and Chief of Bureau. 
<\ L. .M.\ i;i. Air, Entomologist and Acting Chief in Absence of Chief. 
R. S. Clifton. Executive Assistant. 
W. F. Tastet. Chief Clerk. 

F. H. Chittenden, in charge of truck crop and stored product insect investiga- 
tions. 
A. D. Hopkins, in elm rue of forest insect investigations. 
W. P. Hunter, in elm roe of southern field crop insect investigations. 
V. M. Webster, in charge of cereal and f orotic insect investigations. 
A. L. Quaintance, in charge of deciduous fruit insect investigations. 
Iv F. Phillips, in charge of bee culture. 

D. M. Rogers, in charge of preventing sin-cod of mollis, field ivork. 
Kolla P. CuRRIE, in chortle of editorial work. 

Mabel Colcord, in charge of library. 

Southern Field Crop Insect Investigations. 
W. I>. Hunter, in charge. 

F. C. Bishopp, A. H. Jennings, H. P. Wood, W. V. King, engaged in tick life- 
It i. star u investigations. 

W. D. Pierce, G D. Smith, J. D. Mitchell, Harry Pinkus, B. R. Coad, R. W. 
Moreland, engaged in cotton-boll weevil investigations. 

A. C. Morgan, G. A. Runner, S. E. Crumb, D. C. Parman, engaged in tobacco 
instil investigations. 

T. E. Holloway. E. R. Barber, engaged in sugar cane insect investigations. 

E. A. McGregor, W. A. Thomas, engaged in red spider and other cotton insect 
investigations. 

J. L. Webb, engaged in rice insect investigations. 

R. A. Cooley, D. L. Van Dine, A. F. Conradi, C. C. Krumbhaar, collaborators. 



WECtlVEP 



68 



NOV 1 ? 1933 

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Cllh ULAH Nil. 148. Issued April .!<>. 1'JIL'. 



5 

United States Department of Agriculture, 



BUREAU OF ENTOMOLOGY, 
L. O. HOWARD, Entomologist and Chief of Bureau. 



TWO DESTRUCTIVE TEXAS ANTS. 

By W. P. Hunter, 
/// Charge of Southern Field-Crop Insect Investigations. 

THE CUTTING OR PARASOL ANT. 

(Atta texana Buckley.) 

The so-called cutting or parasol ant {Atta texana Buckley) is well 
known to residents of the region in which it occurs. The colonies 
are located in sandy soil, generally in the timber, and consist of low 
mounds of considerable extent covered with numerous craters about 
18 inches in diameter. The ants have the habit of cutting the leaves 
from a great variety of plants and of carrying them to their nests. 
Jn many cases the attack is concentrated on one tree, which may be 
entirely defoliated in a single night. The species is of a reddish- 
brown color. The colonies contain individuals showing great differ- 
ences in size, as will be explained later. 

DISTRIBUTION. 

The range of this species is rather restricted. It is known only 
1'tom a limited area in south-central Texas. This area extends from 
the Brazos River as far north as Waco to the Gulf, westward as far 
as San Antonio, and southward to the vicinity of Alice. The ant is 
most common in the valleys of the Colorado, Guadalupe. Comal, and 
San Antonio Rivers. In these situations it is evidently increasing 
in numbers from year to year. In many cases the nests occupy the 
land practically continuously for many miles up and down the 
\ alleys. 

HABITS. 

The nests consist- of underground chambers with several openings 
or craters. The surplus openings seem to be provided for the pur- 
pose of ventilating the underground passages. The nests are located 
91738 — 22 



2 TWO DESTRUCTIVE ANTS. 

generally in sandy soil. The more compact soils seem to be unfavor- 
able for their construction. A very common location for a colony is 
a sandy promontory, well lighted by the sun, in the bend of a river* 

The large irregular mounds are due to the leveling by the wind 
and rains of the circular ridges of sand, brought from beneath the 
surface, which surround the openings. Consequently, each of the 
mounds is an indication of the activity of the ants for many years. 
Beneath these mounds are numerous chambers connected by narrow- 
passages, and there may be direct connection by these channels over 
an area of several hundred square feet. 

The habits of this insect have attracted great attention from scien- 
tists and others. The ants cut the leaves from trees and carry them 
to the nests. Each leaf is finely divided and made into small pellets. 
In this work the mandibles and legs of the ants are utilized. The 
small masses are placed upon the so-called fungus garden, where 
they furnish a growing medium for the growth of a fungus which 
furnishes the colony with food. As the supply of fungus is con- 
sumed the ants add to the old mass, so that eventually the nests are 
found to contain large spongy formations on the outer portion of 
which the slender threads of the fungus are growing. Evidently 
the ants exercise great care in preventing the contamination of the 
fungus garden by any but the sole species of fungus that is utilized. 

The ant is active throughout the greater part of the year. In 
fact, it becomes quiet for only a very short time when the winter 
cold is most severe.. It is disinclined to work during very hot 
weather. During the cooler months its activity extends throughout 
the day, but during the summer it is confined to the night. The 
distance over which foraging expeditions take place may be "200 
yards or even more. Practically all species of plants seem to be 
suitable for food, although it is noticeable that only one species is 
attacked at a time. Dr. W. M. Wheeler, who has made very careful 
studies of these ants, has noted that the same colony may feed upon 
a wide variety of plants at different times, but he never observed 
the individuals of a colony collecting different varieties at the same 
time. 1 Among cultivated crops, cotton, corn, fruit trees, sorghum. 
and many others are attacked. Among wild plants, forest trees are 
favored, and frequently the Spanish moss is used. The various 
species of oaks seem to be more or less immune, either on account 
of the texture of the leaves or the tannic acid they contain. This 
immunity is by no means absolute, however, as Dr. Wheeler and Mr. 
J. D. Mitchell have observed the ants making use of such rough 
leaves as those of the live oak. 

1 Wheeler, W. M. The Funsus-Orowintr Ants of North America. Bui. Ame-r. Mux. N ir. 
[list., vol. 23, Artie!.' XXXI. pp. 7^rt-74L'. 



TWO DESTRUCTIVE ANTS. 



The colonies of this ant are formed by the flight of the female's to 
some point not far distant from the nest. The queen alights, digs 
beneath the surface, deposits a small quantity of the fungus from the 
original nest, and on it deposits a number of eggs. 

FORMS. 

This ant occurs in five forms, namely, soldiers, large workers 
(media), small workers (minima), males, ami females. The soldiers 
are from 10 to V2 mm. in length, with enormously developed heads. 
The large workers, or media, resemble the soldiers, although the 
head is somewhat smaller, and the length of the body is between 
."> ami !) mm. The small worker forms, called minima, are from 1.5 
to 2..") mm. in length. The head is still smaller than in the media. 
Each of these three forms has a special function in the nest. The 
soldiers are concerned primarily with the protection of the nest. 
They do not sting, but bite with their mandibles, which are strong 
enough to draw blood. The huge workers and small workers are 
busied principally with the gathering f leaves for the fungus garden 
and the preparation of the material on which the fungus grows. The 
remaining forms are the males and females. These are much larger 
than the other forms. The female is about 18 mm. in length. The 
color is dark brown, although the legs are somewhat reddish. The 
body is covered with dense tawny hair. The wings, which are shed 
soon after the flight of the queen, are reddish brown, especially along 
the anterior borders. The males are from 13 to 14 mm. long with a 
head of small size which contrasts greatly with that of the worker 
forms. The body is densely covered with long yellowish hairs, as is 
the case with the females. 

REPRESSION. 

The fact that this ant does not continue to attack one species of 
plant continuously, but changes from one to another at frequent in- 
tervals, causes it to be of less importance in the destruction of vege- 
tation than it would he otherwise. Xevertheless, the damage to grow- 
ing crops is frequently heavy, and complaints have become more 
numerous in recent years on account of the greater abundance of 
the ants. In many places considerable areas of land are not planted 
to crops on account of the danger of attack. In all such situations it 
is necessary to resort to repressive means. 

The best method of control is undoubtedly by means of potassium 
cyanid. 2 Mr. J. D. Mitchell has conducted the experiments upon 

' The use of potassium cyanic! in water solution against ants was first followed by 
Messrs. R. S. Woglum and Wra. Wood. (See Journal of Economic Entomology, vol. 1, 
pp. 348-349, 1908.) Mr. II. O. Marsh has also used it. (See Bui. G4, Pt. IX. C. S. 
Pept. Agr.. Bur. Ent.. pp. 74-78, 1910.) 
91738—22 2 



4 TWO DESTRUCTIVE ANTS. 

which this conclusion is based. He used 9.8 per cent potassium cyanid 
at the rate of 1 ounce to 1 quart of water. After careful mixing this 
liquid was poured into each of the openings in several nests, a quart to 
each opening. In every case it was found that the destruction of the 
colony followed after one or two applications. The cost of this 
method is small, but of course will assume considerable proportions 
in areas where the ants are very numerous. Even under such condi- 
tions it will undoutbedly well pay for the expense and is advised above 
all methods that can be followed. 

The use of carbon bisulphid is not practical on account of the very 
extensive excavations the ants make in the sand. Some may be killed, 
but effective work can not be done unless the insecticide is forced into 
the earth by pressure, and this requires special apparatus. Moreover, 
the expense would be much greater than in the case of the cyanid 
method just described. 

Some years ago certain persons in southern Texas followed the 
destruction of this ant as a regular business. They used sulphur and 
a special apparatus for forcing the fumes into the nests. The ma- 
chine consisted of an oven in which the sulphur was burned. The 
fumes were passed through a pipe by forced draft, and the end of 
this pipe was inserted into the ground in the middle of the colony. 
Before the oven was started all of the openings of the nest were care- 
fully closed. It is said that remarkable success accompanied this 
method. It may be found to be advisable to use this method for 
large areas of the infested lands or where several planters can 
cooperate. 

Mr. C. L. Marlatt has described a method of destruction of ants 
which is in use in Cuba : 

It consists in digging a hole C> feet deep by 3 Or 4 feet wide in the midst of 
the colony. This hole is filled with dry brush and a roaring tire started. Into 
this is then poured a bucketful of powdered sulphur. The opening is closed 
with a large iron plate. Through a hole in the center of this plate air is forced 
down into the burning mass witli a large bellows. 3 

THE AGRICULTURAL OR HILLOCK ANT. 

(Pogonomyrmex barbatus molefaciens Buckley.) 

The nests of the agricultural or hillock ant {Pogononiyrmex bar- 
batus molefaciens Buckley) are conspicuous in the territory in which 
they occur on account of the fact that the ants do not allow any 
vegetation to grow in a circular area about them. The mounds are 
15 inches or more in diameter and are frequently covered with parti- 
cles of earth or sand from beneath the surface which constrast strongly 
with the surrounding soil. The bare areas around the mound may 
be 10 feet or more in diameter. 

See W. M. Wheeler : Ants, their structure, etc.. p. 577, 1010. 



TWO DESTRUCTIVE- ANTS. 



DISTRIBUTION. 



The agricultural unt occurs from the Brazos River westward. 
West of San Antonio it is replaced by closely allied forms. Farther 
north, in Kansas and Nebraska, a distinct species of (P. ocddentalis 
Cress.) occurs. The agricultural ant is conspicuously a resident of 
open places and docs not occur in wooded localities. 

HABITS. 

This ant swarms early in the season, generally after a rain. At 
such times the males and females come out of the nest in great num- 
bers, covering the ground for many feet. Mating takes place at this 
time, after which the females fly away. When they alight their 
wings are cast and they begin to dig a cell for a new colony. The 
males after mating are driven away by the workers or killed if they 
persist in returning to the nest. At the time of this swarming multi- 
tudes of the ants are destroyed by birds and horned lizards. 

Many years ago it was announced that the agricultural ant actu- 
ally plants certain grasses in order to obtain quantities of seed to use 
in provisioning the nests. In fact, it was on this supposition that 
one of the common names which have come into use was given it. 
Upon careful investigation, however, it was found that the ant does 
not plant seed intentionally, although it undoubtedly does so acci-' 
dentally. The facts were brought out by Prof. W. M. Wheeler. The 
seeds of several species of grass and common weeds are taken into 
the nests. When the moisture is too great in the nest some of these 
seeds sprout and thus become unsuitable for food. Under such cir- 
cumstances the ants carry out the sprouted seeds and deposit them in 
the immediate vicinity of the nest where many take root and grow. 
Of course this can not be considered intentional planting of the 
seeds, because the ants deal with the sprouted grain exactly as they 
would with any substance that was unsuitable in their nests; that is. 
they simply carry it out and throw it away. 

DAMAGE. 

The economic importance of the agricultural ant is due to the fact 
that it will not allow vegetation to grow in the immediate vicinity 
of its nest and to its powerful sting which it uses on the slightest 
provocation. If the colonies happen to be in fields such as alfalfa, 
corn, or cotton, the area of loss may amount to considerable, and the 
same is true to a certain degree of pasture and range lands. More- 
over, in fields which are mowed the mounds interfere with the work- 
ing of the machine, and the ants are likely to attack the horses. 
There is some degree of compensation for the loss of the land cleared 
by the ants. It will be noted that in a circle just outside of the area 



6 TWO DESTRUCTIVE ANTS. 

that is cleared the plants grow with great luxuriance. Frequently 
these plants become quite conspicuous in the field. This redoubled 
growth is due apparently to the fact that the underground tunnels of 
the ants loosen up the soil and have somewhat the effect of deep plow- 
ing. It is not likely that the increased growth under these condi- 
tions offsets entirely the loss in the area where no plants are allowed 
to grow, but it is sufficient to reduce the importance of the insect to 
some extent. Mr. J. D. Mitchell, who has made many careful obser- 
vations on this species, believes that the actual damage inflicted is 
generally overestimated. 

The sting of the agricultural ant is at least as severe as that of a 
bumblebee. It is speedily inflicted on any animal that approaches 
the nest. Consequently, colonies located in the vicinity of houses 
or on roads or paths frequently become decided nuisances. The best 
local application for stings are aqua ammonia or bicarbonate of 
soda (baking soda). When fainting or dizziness occurs, as is fre- 
quently the case, a few drops of ammonia taken internally will In 
helpful. 

N ATUK A L E N EMI E S . 

Natural enemies exert some repressive influence upon agricultural 
ants. The most important enemy among the birds is the great- 
tailed grackle (Megaquisccdus major macrourus), commonly known 
as the jackdaw. The following additional Texas birds are known to 
prey upon species of Pogonomyrmex, according to records in the 
Biological Survey: Upland plover (Bartramia longica/iuPa) , burrow- 
ing owl {Speotyto cunicularia hyplogosa), Texas nighthawk (Chor- 
deiles acutipennis texensis), scissor-tailed flycatcher {Muscivora for- 
fc/ff<r), kingbird (Tyrannus tyrannus), redbird (Cardinalis cardi- 
nalis), and mockingbird (Mimus polyglottos). The horned lizard 
(Phrynosoma comutum) includes agricultural ants as a part of its 
regular diet. 

REPRESSION. 

As in the case of the cutting ant. the destruction of this species 
can best be brought about by the use of the solution of potassium 
cyanid in water. Mr. J. D. Mitchell conducted experiments at Vic- 
toria. Tex., which showed that this was a perfectly satisfactory 
method. It is much cheaper and easier of application than in the 
case of the cutting ant on account of the fact that the underground 
portion of the nest is much less extensive. A pint of liquid is suf- 
ficient for even a large colony, though sometimes a second applica- 
tion may be necessary. 

Carbon bisulphid is also a good remedy and can be applied in 
a very simple manner. All that is necessary is to pour about 2 



TWO DESTRUCTIVE ANTS. 7 

ounces into the opening of the nest. The opening need not be closed. 
As the gas in much heavier than air, it sinks into the innermost 
recesses and kills all of the ants in the colony. Setting fire to the 
liquid is of no benefit. In fact, it is likely to lessen its efficiency. The 
poison may be applied at any time of the day, regardless of the 
number of the ants that are outside the nest. The destruction of 
the colony depends upon the killing of the queen, and she remains 
in the nest at all times, except when the swarming flight is under 
way, for a very short time in. the spring. 

Sometimes Paris green or other arsenicals are used in the attempt 
to control this species. They are generally applied by simply pour- 
ing a handful into the openings. Many of the ants are killed, but 
a large part of the brood is not affected, and the colony soon becomes 
as numerous as ever. In some cases where this method has been 
followed persistently the ants have moved their nest a few feet away 
and have become reestablished perfectly in a short time. For these 
reasons the use of arsenicals can not be considered satisfactory. 

Another method sometimes followed, which is of little practical 
use, is trapping the ants in bottles. If a large bottle is buried in the 
ground in the vicinity of the nest with the neck flush with the sur- 
face the ants soon begin an exploration and fall inside. The noise 
they make in the bottle attracts many others. In this way in the 
vicinity of a populous colony a large bottle may be filled in a short 
time. The objection to this procedure is that it only reduces the 
strength of the colony. The immature stages and the queen are not 
affected, and the colony soon regains its former numbers. 

Approved : 

James Wilson, 

Secretary of Agriculture. 

Washington, D. C, January 18, 1921. 



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